In the past two decades, scientists and government agencies have developed methods to identify carcinogenic chemicals, explore cancer mechanisms, and quantify the risks from exposures. There is an increasing lack of consensus among scientists on the application of risk assessment to prevent cancer in humans based on animal bioassays. The United States and European government agencies use substantially different approaches in assessing cancer risks. A relatively small number of chemicals have been identified to be human carcinogens; a large number of chemicals have been proposed to be potential carcinogens in humans based on animal studies. A challenge for scientists is to assess the risks of chemicals accurately in order to provide adequate protection of public health, yet not prevent technological development. The American Health Foundation (AHF) proposes to convene an International Expert Panel comprised of 15 prestigious scientists to address the following issues: Species to Species Extrapolation: The panel will examine the data correlating human cancer and animal tumors. Animal tumor types resulting from stimulation by proliferative agents such as promoters and hormones will be analyzed for their significance to human cancer. Threshold Doses: The Panel will analyze dose-response relations exhibiting thresholds for epigenetic and genetic carcinogens. The Panel will meet twice during 1990. Support is requested for the development of a scientific publication reviewing the literature and reporting the consensus of the Panel to be published in a peer-reviewed journal. The support for meeting expenses will come from AHF funds.